Method of and Apparatus for Forming Three-Dimensional Structures Integral With Semiconductor Based Circuitry

Abstract

Enhanced Electrochemical fabrication processes are provided that can form three-dimensional multi-layer structures using semiconductor based circuitry as a substrate. Electrically functional portions of the structure are formed from structural material (e.g. nickel) that adheres to contact pads of the circuit. Aluminum contact pads and silicon structures are protected from copper diffusion damage by application of appropriate barrier layers. In some embodiments, nickel is applied to the aluminum contact pads via solder bump formation techniques using electroless nickel plating. In other embodiments, selective electroless copper plating or direct metallization is used to plate sacrificial material directly onto dielectric passivation layers. In still other embodiments, structural material deposition locations are shielded, then sacrificial material is deposited, the shielding is removed, and then structural material is deposited. In still other embodiments structural material is made to attach to non-contact pad regions.

1 . An electrochemical fabrication process for producing a three-dimensional structure from at least one structural material on a semiconductor wafer, or portion thereof, from a plurality of adhered layers, the process comprising: 
 (A) supplying a substrate which comprises a semiconductor wafer or portion thereof containing electrical circuitry and having contact pads to which a first conductive structural material is to connect, wherein the substrate may comprise previously deposited material and wherein forming a connection between the contact pads and the first conductive structural material and applying a sacrificial material, comprises: 
 (a) applying a transition coating to the substrate;  
 (b) applying the first conductive structural material to the contact pads over the transition locating by application of an electroless plating solution to the contact pads for a sufficient time to form a deposition of desired thickness;  
 (c) applying a first conductive sacrificial material to the substrate; and  
   (B) forming a plurality of layers, with the first layer of the plurality of layer being formed on the first conductive structural material and the first conductive sacrificial material such that successive layers are formed adjacent to and adhered to previously formed layers, wherein the formation of at least some of the plurality of layers includes a selective depositing operation which deposits at least one of a second conductive structural material or a second conductive sacrificial material;    wherein at least a plurality of the selective depositing operations comprise: 
 (1) forming and adhering a selected mask to a previously formed layer;  
 (2) in presence of a plating solution, conducting an electric current between an anode and the previously formed layer through at least one opening in the mask such that a selected one of the second conductive structural material or the second conductive sacrificial material is deposited onto the previously formed layer to form at least a portion of a layer; and  
 (3) separating the mask from the previously formed layer; and  
   (C) separating at least a portion of the first and second conductive sacrificial materials from the first and second conductive structural materials after formation of the plurality of layers.    
     
     
         2 . The process of  claim 1  wherein after applying the first conductive structural material to the contact pads, the first conductive sacrificial material is applied to the substrate.  
     
     
         3 . The process of  claim 2  wherein the applied first conductive structural material on the contact pads has a thickness less than a desired thickness and is increased to a desired thickness by electroplating.  
     
     
         4 . The process of  claim 2  wherein after application of the first conductive sacrificial material to the substrate, the first conductive sacrificial and structural materials are planarized to yield a modified substrate comprising selective regions of the first conductive sacrificial material and the first conductive structural material on to which layers of the second conductive structural material and the second conductive sacrificial material will be deposited.  
     
     
         5 . The process of  claim 1  wherein the substrate comprises a transition material located on the contact pads.  
     
     
         6 . The process of  claim 5  wherein the transition material comprises an adhesion promoter.  
     
     
         7 . The process of  claim 5  wherein the transition material comprises a diffusion barrier.  
     
     
         8 . The process of  claim 1  wherein the first conductive structural material comprises nickel.  
     
     
         9 . The process of  claim 1  wherein the first conductive sacrificial material comprises copper.  
     
     
         10 . An electrochemical fabrication process for producing a three-dimensional structure form at least one structural material on a semiconductor wafer or portion thereof from a plurality of adhered, the process comprising: 
 (A) supplying a substrate which comprises a semiconductor wafer, or portion thereof, containing electrical circuitry and having contact pads to which a first conductive structural material is to connect, wherein the substrate may comprise previously deposited material and wherein forming at least a portion of a layer onto the substrate comprises: 
 (a) shielding at least the contact pads with a shielding material;  
 (b) depositing a first conductive sacrificial material to unshielded regions using at least one technique selected from the group consisting of (1) direct metallization, (2) direct plating, and (3) electroless deposition;  
 (c) removing the shielding material after deposition of the first conductive sacrificial material; and  
 (d) depositing first conductive structural material onto the contact pads; and  
   (B) forming a plurality of layers, with the first layer of the plurality of layers being formed on the first conductive sacrificial material and on the first conductive structural material, such that successive layers are formed adjacent to and adhered to previously formed layers, wherein the formation of at least some of the plurality of layers includes a selective depositing operation which deposits at least one of a second conductive structural material or a second conductive sacrificial material;    wherein at least a plurality of the selective depositing operations comprise: 
 (1) forming and adhering a selected mask to a previously formed layer;  
 (2) in presence of a plating solution, conducting an electric current between an anode and the previously formed layer through at least one opening in the mask such that a selected one of the second conductive sacrificial material or second conductive structural material is deposited onto the previously formed layer to form at least a portion of a layer; and  
 (3) separating the mask from the previously formed layer; and  
 separating at least a portion of the first and second sacrificial materials from the first and second structural materials after formation of the plurality of layers.  
   
     
     
         11 . The process of  claim 10  wherein after deposition of the first conductive sacrificial material onto the substrate and removal of the shielding material from the contact pads, applying a treatment coating to the contact pads prior to depositing the first conductive structural material.  
     
     
         12 . The process of  claim 11  wherein the treatment coating comprises a material that enhances effective adhesion between the first conductive structural material and the contact pads.  
     
     
         13 . The process of  claim 10  wherein the deposition of the first conductive structural material onto the contact pads comprises electroplating the first conductive structural material onto at least one contact pad via electroplating of the first conductive structural material onto the first conductive sacrificial material wherein a region of deposition of the first conductive structural material expands to bridge a dielectric gap separating the first conductive sacrificial material from the at least one contact pad.  
     
     
         14 . The process of  claim 12  wherein after deposition of the first conductive structural material on the contact pads, the first conductive sacrificial material on the substrate and the first conductive structural material on the contact pads are planarized to yield a modified substrate comprising selective regions of the first conductive sacrificial and the first conductive structural material on to which the plurality of layers comprising the second conductive structural material and the second conductive sacrificial material will be deposited.  
     
     
         15 . The process of  claim 10  wherein the process further comprises applying a transition material to the contact pads.  
     
     
         16 . The process of  claim 15  wherein the transition material comprises an adhesion promoter.  
     
     
         17 . The process of  claim 15  wherein the transition material comprises a diffusion barrier.  
     
     
         18 . The process of  claim 10  wherein the first conductive structural material comprises nickel.  
     
     
         19 . The process of  claim 10  wherein the first conductive sacrificial material comprises copper.  
     
     
         20 . An electrochemical fabrication process for producing a three-dimensional structure form at least one structural material on a semiconductor wafer, or portion thereof, from a plurality of adhered layers, the process comprising: 
 (A) supplying a substrate which comprises a semiconductor wafer, or portion thereof, containing electrical circuitry and having contact pads to which a first conductive structural material is to connect and having at least one region of dielectric material where the first conductive structural material is to adhere, wherein the substrate may comprise previously deposited material, and wherein the adhering of the first conductive structural material to the at least one region of dielectric material and applying a first conductive sacrificial material, comprises: 
 (a) depositing a conductive base material onto the dielectric region,  
 (b) depositing the first conductive structural material to at least a selected location of the base material, and  
 (c) if the base material exists in any regions which are not overlaid by the first conductive structural material, subsequently removing any such base material that is not overlaid; and  
 (d) applying a first conductive sacrificial material to the substrate;  
   (B) forming a plurality of layers, with the first layer of the plurality of layers being formed on the first conductive sacrificial material and on the first conductive structural material, such that successive layers are formed adjacent to and adhered to previously formed layers, wherein the formation of at least some of the plurality of layers includes a selective depositing operation which deposits at least one of a second conductive structural material or a second conductive sacrificial material;    wherein at least a plurality of the selective depositing operations comprise: 
 (1) forming and adhering a selected mask to a previously formed layer;  
 (2) in presence of a plating solution, conducting an electric current between an anode and the previously formed layer through at least one opening in the mask such that a selected one of the second conductive sacrificial material or the second conductive structural material is deposited onto the previously formed layer to form at least a portion of a layer; and  
 (3) separating the selected mask from the substrate; and  
 separating at least a portion of the first and second sacrificial materials from the first and second structural materials after formation of the plurality of layers.